Adjusting the slope on my driveway
July 6, 2020 12:24 PM Subscribe
My wife's car scrapes the bottom coming in our driveway. It doesn't have the usual gutter-dip or concavity of a rolled curb, but appears to be a straight (slanted, steep) run of concrete up to the sidewalk, a level sidewalk, and then a more gentle slope up from the sidewalk. What (if any) product can simply make the slope of the first section gentler?
Here's a picture of my driveway and its interaction with the curb. The sloped section is 25 inches wide (on the oblique) with a height change of 6.5 inches (so its purely horizontal width is a little more than 24 inches, and incline about 27%). At the street side of that slope is a little lip, the same width as the curb is off to the left and right of the driveway; that lip is flat except for a rounded drop off to the street. It's about 2 inches above street level and between 7 and 8 inches wide (it's rounded on the street side, making a definite measurement difficult). Shelley's car scrapes when (I think, it's been a while since we tested this exactly) the front wheels are on the house side of the (flat) sidewalk and haven't quite reached the upwards-sloping part of the driveway on that side.
I've been looking into rubber (and similar nonasphalt, nonconcrete materials) curb ramp additions and it's not clear to me that many of them are what I need. A lot of ramps seem to be in the shape of right triangles, meant to be (or so I assume) placed up against a non-cut curb so that there's a (steep) slope one can roll things up instead of the sharp edge of the curb. Another popular type is meant to fit over a rolled curb — the gold standard among these seem to be the Bridjit brand — and have this rounded top and bottom. But as far as I can tell looking at their specifications, those mean to be installed into a profile which is somewhat concave downwards, into a gutter, and I don't have any downwards concavity in my curb-cut. Some of these brands (particularly Bridjit, who have a fit test here say there should be at least 1.75 inches of inset from the straight-line gap you're trying to bridge. Laying a yardstick between the top of the slope and the contact point at the far end of the street-side lip (which is a lot more than Bridjit's recommended 20 inches) and measuring the distance to the furthest point of the curb, I got something shy of 1.5 inches, which seems not to meet their criteria.
So, given that what's supposed to be the most adaptable standard out there doesn't work for this, what are my options? It seems that what I really want is an extremely oblique triangular prism which could nestle into the slope I have --- say, a triangle with base length 7 inches, and oblique sides of length 25 and 31.8 (if I'm doing my trig right), which could nestle into my 6.5-inch-high and 24-inch-long extant ramp and extend it into a gentler 6.5-inch high and 31-inch long ramp. Naturally, those exact specifications aren't a thing that exists and is sold, so what kind of mass-market thing (or contracted projects, or easy DIY projects) would work here?
Here's a picture of my driveway and its interaction with the curb. The sloped section is 25 inches wide (on the oblique) with a height change of 6.5 inches (so its purely horizontal width is a little more than 24 inches, and incline about 27%). At the street side of that slope is a little lip, the same width as the curb is off to the left and right of the driveway; that lip is flat except for a rounded drop off to the street. It's about 2 inches above street level and between 7 and 8 inches wide (it's rounded on the street side, making a definite measurement difficult). Shelley's car scrapes when (I think, it's been a while since we tested this exactly) the front wheels are on the house side of the (flat) sidewalk and haven't quite reached the upwards-sloping part of the driveway on that side.
I've been looking into rubber (and similar nonasphalt, nonconcrete materials) curb ramp additions and it's not clear to me that many of them are what I need. A lot of ramps seem to be in the shape of right triangles, meant to be (or so I assume) placed up against a non-cut curb so that there's a (steep) slope one can roll things up instead of the sharp edge of the curb. Another popular type is meant to fit over a rolled curb — the gold standard among these seem to be the Bridjit brand — and have this rounded top and bottom. But as far as I can tell looking at their specifications, those mean to be installed into a profile which is somewhat concave downwards, into a gutter, and I don't have any downwards concavity in my curb-cut. Some of these brands (particularly Bridjit, who have a fit test here say there should be at least 1.75 inches of inset from the straight-line gap you're trying to bridge. Laying a yardstick between the top of the slope and the contact point at the far end of the street-side lip (which is a lot more than Bridjit's recommended 20 inches) and measuring the distance to the furthest point of the curb, I got something shy of 1.5 inches, which seems not to meet their criteria.
So, given that what's supposed to be the most adaptable standard out there doesn't work for this, what are my options? It seems that what I really want is an extremely oblique triangular prism which could nestle into the slope I have --- say, a triangle with base length 7 inches, and oblique sides of length 25 and 31.8 (if I'm doing my trig right), which could nestle into my 6.5-inch-high and 24-inch-long extant ramp and extend it into a gentler 6.5-inch high and 31-inch long ramp. Naturally, those exact specifications aren't a thing that exists and is sold, so what kind of mass-market thing (or contracted projects, or easy DIY projects) would work here?
Also noting that the picture link doesn't work, but if I could see it and it looked like the standard kind of driveway apron that goes up to a sidewalk that's separated from the street by a parkway, it might not actually be on your property so the legality of altering it in any way could be iffy.
posted by LionIndex at 12:47 PM on July 6, 2020 [1 favorite]
posted by LionIndex at 12:47 PM on July 6, 2020 [1 favorite]
Response by poster: Sorry about the link; this should work.
posted by jackbishop at 1:14 PM on July 6, 2020
posted by jackbishop at 1:14 PM on July 6, 2020
Yeah, that's a pretty narrow parkway, so your apron has to get to curb height in a short distance. Looks like a fairly old neighborhood? Has anyone else in the area tried to solve this problem?
posted by LionIndex at 1:21 PM on July 6, 2020 [1 favorite]
posted by LionIndex at 1:21 PM on July 6, 2020 [1 favorite]
It would help if you could determine exactly when the scraping occurs -- the exact position of the front wheels and the back wheels when contact is made.
From the picture I'm guessing that the scraping is occurring at the sharp edge between the sidewalk and the street side of the driveway while your rear wheels are in the street and the front wheels are on the sidewalk. If that is the case, there isn't anything minor you can do because it means you need to raise the level out in the street. The alternative is to lower the sidewalk a couple of inches, but that is going to require city approval and likely expensive.
There aren't visible signs of a lot of scraping on the sidewalk so it might be that it is just barely marginal. You may find that you can avoid scraping by delicate driving technique to avoid the car bouncing up and down. Slow and easy and going straight in and out, not at an angle.
posted by JackFlash at 1:28 PM on July 6, 2020
From the picture I'm guessing that the scraping is occurring at the sharp edge between the sidewalk and the street side of the driveway while your rear wheels are in the street and the front wheels are on the sidewalk. If that is the case, there isn't anything minor you can do because it means you need to raise the level out in the street. The alternative is to lower the sidewalk a couple of inches, but that is going to require city approval and likely expensive.
There aren't visible signs of a lot of scraping on the sidewalk so it might be that it is just barely marginal. You may find that you can avoid scraping by delicate driving technique to avoid the car bouncing up and down. Slow and easy and going straight in and out, not at an angle.
posted by JackFlash at 1:28 PM on July 6, 2020
Another possibility is to go to a tool rental and get an angle grinder with a concrete head and use it to put a one inch bevel on the sharp edge between sidewalk and driveway. Again, you need to determine the exact geometry of your car and where it scrapes.
posted by JackFlash at 1:41 PM on July 6, 2020
posted by JackFlash at 1:41 PM on July 6, 2020
Slow and easy and going straight in and out, not at an angle
and if that doesn't work, try a much more extreme angle so that the car goes kind of crabwise up the ramp and across the sidewalk. That will put two of its wheels closer to the apex of the bump than they would be on a straight-in path, which might be just enough to let the underside clear it.
I drive a Daihatsu Mira kei car that has tiny little wheels and not much ground clearance, and that's the technique that works for me on terrain like what's in your picture.
In any case, dead slow.
posted by flabdablet at 2:12 PM on July 6, 2020 [2 favorites]
and if that doesn't work, try a much more extreme angle so that the car goes kind of crabwise up the ramp and across the sidewalk. That will put two of its wheels closer to the apex of the bump than they would be on a straight-in path, which might be just enough to let the underside clear it.
I drive a Daihatsu Mira kei car that has tiny little wheels and not much ground clearance, and that's the technique that works for me on terrain like what's in your picture.
In any case, dead slow.
posted by flabdablet at 2:12 PM on July 6, 2020 [2 favorites]
Also useful would be the make and model of car giving you the problem. From that you can determine if it has unusually low ground clearance.
posted by JackFlash at 2:39 PM on July 6, 2020
posted by JackFlash at 2:39 PM on July 6, 2020
As a "temporary" (ie, doesn't need approval from city for modifying the sidewalk or street) you could construct some ramps like I have painstakingly :) sketched here. They could be stashed at the side of the drive and used as needed. Obviously a pain, but would potentially work.
There are all sorts of caveats about this idea, including:
* The narrower the ramps, the harder they are to "hit" and the more straight-on your approach has to be
* The wider the ramps, the heavier they will be and the more expensive the lumber will be
* In an ideal world, the ramps would be solid, with no "air" under them at any point, sawn to match the pavements they lay on. That aside, I would want no more than a foot of unsupported board, hence my "braces", which need to touch the ground or be within a smidge of it (the board will flex, but not a lot, maybe an eighth of an inch?
* You'd ideally make the ramps as short as is practical, but not so short you've only left two microns under the car at the sill's closest approach
* I am not an engineer. I do think a 2" board 12" wide will support the weight of a quarter of a car over one foot of unsupported air (ie, between braces) but doing the math would be good
You can buy loading ramps, some fairly wide, made of aluminum mesh, for motorcycles and such, and you might look if one of those would be a professional version of what I have sketched.
If you want a permanent solution, you'd essentially be making a curb cut (like for a crosswalk), except the street edge would not be at street level--it would potentially lower the outer edge of the sidewalk by four inches, which would be enough, I think.
The city is probably not going to be excited by a homeowner doing it, but maybe, and there will be permits and possibly a comment period, etc.
posted by maxwelton at 3:06 PM on July 6, 2020
There are all sorts of caveats about this idea, including:
* The narrower the ramps, the harder they are to "hit" and the more straight-on your approach has to be
* The wider the ramps, the heavier they will be and the more expensive the lumber will be
* In an ideal world, the ramps would be solid, with no "air" under them at any point, sawn to match the pavements they lay on. That aside, I would want no more than a foot of unsupported board, hence my "braces", which need to touch the ground or be within a smidge of it (the board will flex, but not a lot, maybe an eighth of an inch?
* You'd ideally make the ramps as short as is practical, but not so short you've only left two microns under the car at the sill's closest approach
* I am not an engineer. I do think a 2" board 12" wide will support the weight of a quarter of a car over one foot of unsupported air (ie, between braces) but doing the math would be good
You can buy loading ramps, some fairly wide, made of aluminum mesh, for motorcycles and such, and you might look if one of those would be a professional version of what I have sketched.
If you want a permanent solution, you'd essentially be making a curb cut (like for a crosswalk), except the street edge would not be at street level--it would potentially lower the outer edge of the sidewalk by four inches, which would be enough, I think.
The city is probably not going to be excited by a homeowner doing it, but maybe, and there will be permits and possibly a comment period, etc.
posted by maxwelton at 3:06 PM on July 6, 2020
This article reviews various ramp options. It looks like the ones for rolled curbs and raised garage floors might work for you.
In general, you need to put some extra height either right before that short little ramp begins, or right after. Both are problematic for various reasons, but those ramp recommendations at least give you something to work with.
Also I will add that you might experiment with a temporary solution just ot see what works. Like put a length of two-by-four, or some other similar scraps of lumber, just in front of the ramp, or at the base of it, etc. If you can figure out exactly where you need that extra 1-2 inches of height then you can work on a more permanent solution for filling that space (or, maybe you just leave a 2x4 in that spot permanently).
I would also 2nd the idea to just drive in at an angle; that is a very common way of dealing with such situations.
posted by flug at 6:02 PM on July 6, 2020
In general, you need to put some extra height either right before that short little ramp begins, or right after. Both are problematic for various reasons, but those ramp recommendations at least give you something to work with.
Also I will add that you might experiment with a temporary solution just ot see what works. Like put a length of two-by-four, or some other similar scraps of lumber, just in front of the ramp, or at the base of it, etc. If you can figure out exactly where you need that extra 1-2 inches of height then you can work on a more permanent solution for filling that space (or, maybe you just leave a 2x4 in that spot permanently).
I would also 2nd the idea to just drive in at an angle; that is a very common way of dealing with such situations.
posted by flug at 6:02 PM on July 6, 2020
3rd'ing @flabdablet and @flug 's suggestion of coming in at an angle. First, try an experiment: instead of turning 90° from the street into your driveway, only turn 45° and stop when both wheels are on the sidewalk. If you still scrape that way, when you are going to need a physical modification and behavior modification (coming in at an angle) won't work. If you don't scrape during this little 45° experiment, then do the 2nd 45° turn, continuing up your driveway. To recap: try breaking your 90° turn into 2 separate 45° turns, so that only one front wheel is on the first slope at a time, and so that only one front wheel is on the sidewalk at a time.
posted by at at 4:53 AM on July 7, 2020
posted by at at 4:53 AM on July 7, 2020
This thread is closed to new comments.
It's hard to tell from your description here what exactly the problem is, but this is something that i'd check to see if:
1) Can be avoided through a behavior change, e.g. angle of attack when pulling into driveway, or approaching the driveway at a much slower speed
2) Something an asphalt/driveway paving contractor would have a solution for.
The ramp idea could work, but it sounds like it's not going to be a permanent one - I've definitely seen well-design car ramps made out of plywood and lumber that could be customized to to the issue you're describing, but I'd think it's usage still requires behavior change and it's not a permanent solution.
posted by Karaage at 12:44 PM on July 6, 2020